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Thread: Brand New Generator Low Voltage

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    Freshman Member TAS525's Avatar
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    Brand New Generator Low Voltage

    After only the first drive of the season, the generator on TS43172LO gave up the ghost. Following testing, I decided to replace, along with the original control box. Ordered new generator from a usual suspect (Told these are more reliable than another rebuild) and after weeks of waiting for the back ordered part I finally installed and polarized (positive ground) yesterday.

    I knew I would have some adjustments to make since the ammeter was pegged at - 30 amps and the cutout remained closed even after shutdown (why?), but decided to sleep on it.

    Today, Lucas Manual in hand, I began the series of tests, only to stop on Test 3 with a mere .5 volt registering from the generator (revs between 800 & 1500). Please tell me this is operator error and that I donít have to return this unit from whence it came! Iím no EE major, and these are relatively simple tests, so please let me know what I am overlooking. I even retightened the belt, thinking 3/4Ē might be too loose! Made no difference whatsoever.
    Last edited by TAS525; 06-14-2020 at 06:54 PM.

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    Yoda
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    Re: Brand New Generator Low Voltage

    Not had much to do with the old control boxes in years but I seem to remember they sometimes needed the contact cleaned.
    There may be an electronic replacement for the old control box.

    David
    TR3A TS75524L

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    Obi Wan Sarastro's Avatar
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    Re: Brand New Generator Low Voltage

    You may not be an EE (I am) but you can think like one. First thought should be to isolate the problem. Keep isolating it, and before long you'll have it cornered like a scared rabbit.

    Start with the generator. disconnect it, both the D and F connections. Then connect them together. Measure the voltage at the D/F of the generator as you run the engine up to 2000 RPM or so. It should easily put out 20 volts or so. If it does, it's probably OK. If it doesn't, it's definitely bad.

    Next, check out the control box. Pop the top off and make sure that the contacts are not welded together. Look under it and make sure that nothing is fried. If it looks OK, and it's new, it probably is OK.

    If those check out, I suspect you have a wiring error. Pinning the ammeter is pretty drastic, and you may have fried something. Look for discolored wiring or melted insulation, and fix anything like that.

    I think that will get you started.
    Steve Maas
    1966 Triumph TR4A, undergoing restoration: http://www.nonlintec.com/tr4a
    1952 MG TD, restoration completed 2014, sold 2016: http://www.nonlintec.com/mgtd
    1960 Austin-Healey "Bugeye" Sprite, sold 2010: http://www.nonlintec.com/sprite
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    Yoda CJD's Avatar
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    Re: Brand New Generator Low Voltage

    I have tried to read through the control box setting procedure in the manual, but I cannot find step 3. All I see for step 3 is to reconnect the A wire...which couldn't be your stopping point. Which page and paragraph are you going by, so we can all be on the same page? Remember that, if the cutout is not working, best to disconnect the battery before leaving the car for very long, as it will be drawing current and energizing the generator field if you don't.

    If the ammeter pegged at -30, I suspect something is not wired correctly. That is reading a draw, which is not a generator issue unless something is grounded in the wiring or you polarized backwards. Of note, these little generators are only rated to 21 amps, and they start slinging solder if held above that for more than a few seconds.

    The entire system is super simple. There are only 2 adjustments in the control box...you set the field to control voltage output, and you set the cutout to, well, cutout at the proper voltage when generator output is stopped with the engine motion. Mis-wiring is the most likely issue at the moment.

    What Steve suggests will check your generator, which is a good start-over point. Then triple check connections at the control box and let us know which setting procedure you are using.
    John

    1955 TR2

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    Freshman Member TAS525's Avatar
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    Re: Brand New Generator Low Voltage

    Thanks fellas. This problem came about as a result of a steady ignition light beginning last season. This May, following the first seasonís drive, the light again came on, but this time after switching off the ignition, indicating the cut out was still closed, which it was. After checking connections (D terminal on generator was loose), testing for generator output (nil) and referencing my Dadís maintenance log (This was the 3rd generator since the carís Ď92 rebuild and it was previously overhauled), I decided to swap out both the Dynamo and Control Box (original).

    The box is from one supplier, the new Generator from another. Using the maintenance manual, I have adjusted and cleaned the regulator and cut out. I installed and polarized the generator for positive ground and adjusted the fan belt for 1/2Ē play.

    I was prepared to start the car and set the voltage and enjoy whatís left of the summer but not for this! Should know by now to lower my expectations.

    The tests Iíve referenced are from the Lucas Fault Diagnosis Service Manual pg 27 (Dynamos and Control Boxes). To my disbelief and chagrin, both tests 3 and 4 have failed, with the generator producing a mere .37 - to .5 volts.

    I think Iím just in denial that a brand new generator could be DOA, but I see no reason to proceed with tracing down faulty wiring, adjusting gaps, etc if my generator wonít even spool up. Iíll start over in a few days (wife says itís time for a family trip to - ANYWHERE!). I also have a feeling the dynamo isnít really polarized/excited, because I havenít been able to get a spark when I connect field to ďhot sideĒ (side connected to starter solenoid) of battery. Wouldnít that also account for the lack of output?

    Thank yíall for the advice and please let me know if there is something I am missing before I start making angry phone calls to the parts supplier!

    BTW, the battery has been disconnected following these tests and is the only way to ensure the cutout opens (it is still closing upon shutdown) as to prevent drainage.

    Thanks again!

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    Yoda
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    Re: Brand New Generator Low Voltage

    When I was going through some problems like you have, I used my impact gun and spun the generator on my work bench to measure the voltage output and it worked for me. I could watch the voltage go up and down with my inexpensive HF volt meter. If you have no output, I would pop the back cover off and have a look at the brushes. Maybe you are case grounding or something. At least by spinning the generator off the car you will know what you have in your hand.

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    Yoda CJD's Avatar
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    Re: Brand New Generator Low Voltage

    I don’t have the Lucas manual, so not real sure what it has you doing that is failing.

    I can say I am a bit concerned, as it sounds like you may have only had a control box problem to start with. And that may have only been dirty, sticking contacts. Test the original generator as Steve suggests to make sure it was bad.
    John

    1955 TR2

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    Freshman Member TAS525's Avatar
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    Re: Brand New Generator Low Voltage

    Thanks John, the manual is available online and has been referenced in other threads. If you didnít notice in my previous post, I tested the old generator in the vehicle. It would neither produce voltage, nor spin up when connected directly to my battery. It does, however, produce a clicking sound when turned counter clockwise by hand and the D terminal is dangling! The original control box may be fine (I only cleaned the points), but based on the recommendation to swap both units and the aforementioned fact that three generators have destroyed themselves, I decided to replace it as well.
    Last edited by TAS525; 06-16-2020 at 09:50 PM.

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    Freshman Member TAS525's Avatar
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    Re: Brand New Generator Low Voltage

    Well, looks like I may have let a little too much smoke out! After much pondering, I remained convinced that I wasnít polarizing the generator. In the past, I always connected the field directly to the battery, but just wasnít getting a good spark this time. Decided to short the control box and that did the trick, much to my relief! With the generator now producing ample voltage, I proceeded with the remainder of the tests. All seemed to be going well until I got to the cut-out. I just could not get the adjustment right (mind you Iím solo here and constantly being interrupted by any one of 4 children). The cutout never really closed properly. The ignition warning light would extinguish after startup, but then would become dim and even increase slightly in brightness with higher revs. While attempting to determine the cut in voltage, I noticed the contacts would arc and never really close. Finally, after hours of tinkering, I thought perhaps I should try a quick road test and realized that was a bad idea. As soon as I left my driveway, the engine began missing terribly. I wheeled back into the garage and started again from square one. Generator voltage - fine, regulator - perfect. Test 8 however (Lucas Generator and Control Box Tests) failed, and so I decided to give up for the day. Ignition off, warning light extinguished, I began collecting my tools when I noticed smoke, an acrid smell and the sound of arcing from somewhere near the generator. I quickly disconnected the battery, but Iím afraid I may have toasted my generator. HELP!!!

    ...To be continued.

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    Yoda CJD's Avatar
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    Re: Brand New Generator Low Voltage

    The cutout should be a simple adjustment. Start the motor and set it with the choke to at least 1500rpm. Make certain the cutout has closed. If it has not closed, no Big deal, as you are going to open them anyway. Make certain your voltage is set between 13.5 and 14 volts using a volt meter at the battery posts. Any less and the battery will not charge well...any more and you will tend to boil out the water on long trips. If you cannot get the voltage stable in this range, then you have a regulator or generator issue.

    Back to the cutout:

    Loosen the lock nut on the cutout and back off the adjustment until the cutout opens and the red light on the dash comes on (at least 1500 rpm still set). Now, slowly turn the adjuster until the cutout snaps shut. Once it does close, set the lock nut. Remember which direction you had to turn the adjuster to engage the cutout.

    Now, push the choke in and make sure the cutout does not open As the engine idles. If it does, reset the adjustment a quarter turn in the direction you remembered above. Rev the motor to cut it back in, and make sure it stays closed when the rpm drops again. Repeat until it does not drop out at idle.

    The final check is to turn off the motor and ensure the cutout opens within a couple seconds. If it does not, turn your adjustment slightly opposite the direction remembered above. Start the motor and re-check that it cuts in by 2000rpm, remains in at idle, and cuts out at engine stop.

    At most this is a 5 minute job. If you cannot get it set, then there is something off with the control box...sticking contacts, dirty contacts, open coil, etc.
    John

    1955 TR2

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    Freshman Member TAS525's Avatar
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    Re: Brand New Generator Low Voltage

    Thanks John. Mind you, the box is a newer type and doesnít have the lock nut arrangement, but springs that keep the adjustment screws set. I have gapped and cleaned (To the best of my ability) according to the Service Manual, so it really blew my mind that the cut out points kept arcing and never really snapped closed. As long as I didnít sling solder in the generator, I suppose Iíll try adjusting again today using the method you suggested. Will report back.

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    Freshman Member TAS525's Avatar
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    Re: Brand New Generator Low Voltage

    Also... noticed threads referencing ground wire for the Control Box. Pulled the battery and battery box. Sure enough, the wire and connection had been painted over during a botched engine bay job my dad farmed out some 30 years ago! Not sure if it will make any difference, but Iíll clean and reattach just in case this might be creating additional problems.

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    Re: Brand New Generator Low Voltage

    Is there a chance you’re confusing the regulator contacts for the cutout? The regulator cycles regularly While the engine is running, but the cutout should not.
    John

    1955 TR2

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    Re: Brand New Generator Low Voltage

    There is ALWAYS a chance! In this case, however, no.
    Tommy

    1959 TR3A TS43172LO (1959 - Present)

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    Re: Brand New Generator Low Voltage

    Since we're talking about generators, voltage and the control box (regulator), I thought you all might find the following interesting. I just purchased, off eBay, a binder of supplementary service information to the TR2-3 service manual. On June 27, 1960, the mid-Atlantic S-T distributor issued the following bulletin regarding "TR-3 Modified Generator and Regulator." It states:

    "At Engine #TS59289, the Generator, Part No. 205939 (Type C39 19 Amp) and matching Regulator, Part No. 102766 were replaced by a generator of increased capacity, Part No. 203252 (Type C40 23 Amp.) and matching regulator, Part No. 122089.

    "From a service point of view, it is important to note that the generators and matching regulators are interchangeable in Pairs but a new type generator must not be used with the older regulator or vice versa."

    I never knew the regulators/control boxes differed, nor were not interchangeable.
    Keith
    1962 TR4 CT7491L (2020-)
    1957 TR3 TS20447LO (2017-)
    1962 TR3B TCF1183L (1979-1982)
    1966 Spitfire MKII (1972-1975)

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    Freshman Member TAS525's Avatar
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    Re: Brand New Generator Low Voltage

    Interesting, Keith. After researching this very issue, I felt like this has been the cause of the multiple generator problems the vehicle has suffered in the past. This led me to swapping the control box along with the generator, but it sure has become a Pandoraís Box!

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    Re: Brand New Generator Low Voltage

    Honestly, these are very simple units. Assuming they are hooked up correctly. There are only 2 adjustments...set voltage with one...then set cutout with the other. If it takes more than 5 minutes, then something is amiss.
    John

    1955 TR2

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    Re: Brand New Generator Low Voltage

    Can you post some pictures of your new generator and control box? Is it one of the new-built units from India, which probably is a C40, or a newly rebuilt Lucas. If you have a C39 unit, it can get overheated if mated with a control box designed for the higher-output C40. Randall has run into this and I think its because the voltage regulator side has a few coils that allows output current to factor in to voltage regulation.

    The cut-out doesn't really regulate current; it puts the generator in the system as voltage climbs and opens when the car is shut off (or idle speed drops really low). If you manually close the points with the car off, you get a giant spark as the battery discharges through the armature. Of course who would do that...

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    Freshman Member TAS525's Avatar
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    Re: Brand New Generator Low Voltage

    Okay, I decided to start fresh with a new battery and cables (clamp style - why hadnít I done this years ago? Much better contact and so much easier to remove!). Plug inspection revealed serious fouling and led me to suspect the time spent tracing electrical gremlins with the choke on was the cause of the hesitation and back firing. Cleaned the plugs and ops checked good. Fired up today no problem. Generator and regulator both operated normally (Thank God! What I mistook for smoke/smell/arcing was actually steam escaping from a hose or somewhere in the cooling system.) and sent around 13.5 - 14 volts to the battery. The cut out, however, still eludes me. No matter the adjustment, cleaning, etc., it refuses to fully close with an increase in engine speed (ammeter reads normal at initial road speed - plus 5 -10 amps) but remains closed upon shutdown! Contacted MM Tech and asked for advice. Said theyíd send me another control box (these are Chinese manufactured) free of charge and insists the units do not require any adjustment, contrary to their own tech videos. Iíll continue troubleshooting this ďtroublesomeĒ cutout in the meantime and thanks to all for the suggestions. Wish one of you could drop by and see this for yourselves! Dad and I used to joke that a simple, 10 minute project for the average mechanic would take us at least an hour! Iíve been at it now for close to 10!
    Last edited by TAS525; 07-03-2020 at 01:55 PM.

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    Freshman Member TAS525's Avatar
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    Re: Brand New Generator Low Voltage

    Good news! Finally got the cutout to work (I.e., Points now close at idle and open upon shutdown). On the downside, Ignition Warning Light comes on dim around 2000 RPM and remains dim throughout power range. Ammeter shows slight positive charge while driving and voltmeter reads 12.5 or so at the battery, so itís not quite getting what it needs (assuming it should be charging around 14 volts). Generator is pushing around 16.5 at appx 85-90 degrees F outside. Ideas?

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